here is detailed english article about it and the producers, first 3 series was "Vienna Arsenal" and last series was "Deutsche Eisenwerke " they mention there Alkett as designer,
https://tanks-encyclopedia.com/ww2/nazi_germany/sturmpanzer-iv_brummbar.php


I think it's called the Sturmpazer 43 but also as Sturmpanzer IV and the TAMYA model caling it Sturmpanzer IV
https://www.scalemates.com/kits/tamiya-35353-brummbaer--1076227

this means this one needs corrected
https://www.imcdb.org/vehicle_549609-Nibelungenwerk-Sturmpanzer-IV--Brummbar--1943.html